Autor(es):
Ribeiro, Cláudia Correia da Silva, 1974- 
Data: 2008
Identificador Persistente: http://hdl.handle.net/10451/1541
Origem: Repositório da Universidade de Lisboa
Assunto(s): Aquacultura; Teses de doutoramento
Detalhes do Documento
Comparison of rocky reef fish communities among protected, unprotected and arti...
Descrição
Tese de doutoramento em Biologia (Biologia Marinha e Aquacultura), apresentada à Universidade de Lisboa através da Faculdade de Ciências, 2008 This study concentrates on fish species associated to rocky inshore reefs of thesouth coast of Madeira Island in order to obtain base-line data on the structure of thefish assemblages inhabiting the very limited shallow coastal habitats surroundingMadeira Island. The faunistic features of the local fish communities were defined interms of species richness and composition; abundance; trophic, spatial and demographicstructure; and seasonal changes relating to type of substrate, depth, seasons andlocations. Three visual-census methods commonly used in similar studies performedelsewhere (transect, point-count PC and visual fast count - VFC) were used for fishassessment with further comparison and evaluation of efficiency and performance foreach of them and other methods. I determined the extent to which Garajau MarineReserve (GMR) protected different assemblages of reef fishes, the effects of riprapalong the shore of the island as fish habitat, and how protection and artificial substatecan be used in the management of inshore fish resources of Madeira Island. Censuses were seasonally conducted (three times/season) during a two-yearperiod from Spring 2002 to Spring 2004 in three locations on the south coast of MadeiraIsland, including a marine protected area (GMR), a natural non-protected area (Caniçal) and an artificial non-protected area (riprap of Madeira airport). Methods comparison showed that the total number of species recorded by theVFC was always higher than PC and transects methods in all locations, including allbottoms types and both depth; however the use of standard methods such as transect orpoint count are valuable for obtaining fish densities estimates and should be used in a future monitoring program. Diurnally active fishes (61 taxa), belonging to 33 families were recorded. Mostof the families were represented by a single species and five families included about80% of the total of species observed. Considering the total number of species andfamilies recorded in this study, the pattern of fish species diversity in Madeira Islandwas relatively low when compared with littoral areas of tropical and subtropical islandsin the Atlantic. This reinforces the statement that fish diversity characteristicallydecreases from tropical to temperate latitudes. The fact that Madeira Island has oceanicand oligotrophic surrounding waters coupled with the nearshore environment alterationsarisen from increased tourism development and the over-exploitation of fishery resources through the use of very destructive fishing practices, as happened in theneighbour Canarian archipelago, can explain the reduced species diversity. From the overall list of species observed, 34 appeared in the entire area of study,revealing high level of similarity in species composition among areas. There was aspecial-temporal dominance of a small group of species, which composed the group ofcommon species, whatever the location or any other factor considered in the samplingdesign. In that group of species were included: Abudefduf luridus, Chromis limbata,Thalassoma pavo, Sphoeroides marmoratus, Sparisoma cretense, as the most commonand abundantly observed. Moreover, the percentage of rare species in the entire area ofstudy was high; 27 species appeared in less than 25% of the visual counts. Depth and season were significant factors affecting species composition andabundance, but reserve designation did not significantly affect total abundance or meannumber of species observed. The present results indicate that species composition andstructure of the fish communities inhabiting the rocky reefs of Madeira Island wereinfluenced by reef type, namely natural vs artificial, and the total number of species andthe abundance of some demersal species observed in the artificial riprap of Madeira airport were less than in the natural locations studied. Total abundance inside the reserve was less than in fished areas, mainly due tothe presence of large schools of pelagic species outside the reserve. Though the resultsof this study showed that temporal trend in species richness was not affected by reserveeffect, the sites examined in GMR have to some extent met the objective of preservingsignificantly higher number of matured-sized fish and thereby showing potentialspawning stock. Additionally, considering just demersal fish abundance, several species,particularly exploited species such as Sparisoma cretense and Mycteroperca fusca, weremore abundant and with higher frequency of occurrence inside the reserve and thedusky grouper, a widely targeted species across its range was exclusively recorded inside the reserve area, but with very low frequency and abundance. Although this study provided base-line data for ecological management purposesit is essential that further quantitative studies be conducted on densities, size structure aswell in settlement and recruitment processes, to fully acknowledge the inshore fish communities inhabiting the island. The paucity of information obtained till date on reef fish communities ofMadeira Island can be highlighted as a failure in the establishment and assessment ofthe effects of human activities on coastal reefs resources. Hence, the combination present results with the existing from few previous works will help understanding of the coastal reefs communities of Madeira Island. O presente trabalho visou o estudo das comunidades de peixes dos recifesrochosos da costa Sul da Ilha da Madeira com a finalidade de obter dados de referênciasobre a estrutura dos ictiopovoamentos que habitam a estreita faixa rochosa do litoralmadeirense. As comunidades foram caracterizadas em termos de riqueza específica,composição, abundância, estrutura trófica, espacial, demográfica e dinâmica sazonal,considerando os factores profundidade, tipo de substrato e localidade. Utilizaram-se trêsmétodos de contagem visuais (transecto, ponto fixo e visual fast count ),frequentemente utilizados em estudos semelhantes realizados noutras regiões do planeta,mas que aqui foram pela primeira vez aplicados em simultâneo, testando a suaeficiência e desempenho para avaliação das comunidades de peixes existentes, bemcomo uma revisão e actualização acerca deste tipo de metodologias. Avaliou-se o graude protecção das comunidades ictiológicas da Reserva Marinha do Garajau, estimandoos eventuais benefícios das medidas de protecção existentes e investigou-se também ainfluencia de determinadas intervenções humanas como é o caso da implantação deenrocamentos ao longo do litoral madeirense na estrutura das comunidades ictiológicasque estes locais agregam. Pretendeu-se também avaliar e evidenciar uma lista dosmaiores problemas associados à gestão dos recursos ictiológicos costeiros da Ilha daMadeira, identificando os parâmetros mais adequados a serem usados em decorrentesprojectos de monitorização dessas comunidades. O período de amostragem decorreu entre a Primavera de 2002 e a Primavera de 2004, em três localidades da costa Sul da Ilha da Madeira, numa área marinha protegida - Reserva Marinha do Garajau; uma área natural não protegida - Caniçal e uma área costeira submetida a intervenção humana, artificial - o enrocamento do aeroporto da Madeira.
Tese de doutoramento em Biologia (Biologia Marinha e Aquacultura), apresentada à Universidade de Lisboa através da Faculdade de Ciências, 2008 This study concentrates on fish species associated to rocky inshore reefs of thesouth coast of Madeira Island in order to obtain base-line data on the structure of thefish assemblages inhabiting the very limited shallow coastal habitats surroundingMadeira Island. The faunistic features of the local fish communities were defined interms of species richness and composition; abundance; trophic, spatial and demographicstructure; and seasonal changes relating to type of substrate, depth, seasons andlocations. Three visual-census methods commonly used in similar studies performedelsewhere (transect, point-count PC and visual fast count - VFC) were used for fishassessment with further comparison and evaluation of efficiency and performance foreach of them and other methods. I determined the extent to which Garajau MarineReserve (GMR) protected different assemblages of reef fishes, the effects of riprapalong the shore of the island as fish habitat, and how protection and artificial substatecan be used in the management of inshore fish resources of Madeira Island. Censuses were seasonally conducted (three times/season) during a two-yearperiod from Spring 2002 to Spring 2004 in three locations on the south coast of MadeiraIsland, including a marine protected area (GMR), a natural non-protected area (Caniçal) and an artificial non-protected area (riprap of Madeira airport). Methods comparison showed that the total number of species recorded by theVFC was always higher than PC and transects methods in all locations, including allbottoms types and both depth; however the use of standard methods such as transect orpoint count are valuable for obtaining fish densities estimates and should be used in a future monitoring program. Diurnally active fishes (61 taxa), belonging to 33 families were recorded. Mostof the families were represented by a single species and five families included about80% of the total of species observed. Considering the total number of species andfamilies recorded in this study, the pattern of fish species diversity in Madeira Islandwas relatively low when compared with littoral areas of tropical and subtropical islandsin the Atlantic. This reinforces the statement that fish diversity characteristicallydecreases from tropical to temperate latitudes. The fact that Madeira Island has oceanicand oligotrophic surrounding waters coupled with the nearshore environment alterationsarisen from increased tourism development and the over-exploitation of fishery resources through the use of very destructive fishing practices, as happened in theneighbour Canarian archipelago, can explain the reduced species diversity. From the overall list of species observed, 34 appeared in the entire area of study,revealing high level of similarity in species composition among areas. There was aspecial-temporal dominance of a small group of species, which composed the group ofcommon species, whatever the location or any other factor considered in the samplingdesign. In that group of species were included: Abudefduf luridus, Chromis limbata,Thalassoma pavo, Sphoeroides marmoratus, Sparisoma cretense, as the most commonand abundantly observed. Moreover, the percentage of rare species in the entire area ofstudy was high; 27 species appeared in less than 25% of the visual counts. Depth and season were significant factors affecting species composition andabundance, but reserve designation did not significantly affect total abundance or meannumber of species observed. The present results indicate that species composition andstructure of the fish communities inhabiting the rocky reefs of Madeira Island wereinfluenced by reef type, namely natural vs artificial, and the total number of species andthe abundance of some demersal species observed in the artificial riprap of Madeira airport were less than in the natural locations studied. Total abundance inside the reserve was less than in fished areas, mainly due tothe presence of large schools of pelagic species outside the reserve. Though the resultsof this study showed that temporal trend in species richness was not affected by reserveeffect, the sites examined in GMR have to some extent met the objective of preservingsignificantly higher number of matured-sized fish and thereby showing potentialspawning stock. Additionally, considering just demersal fish abundance, several species,particularly exploited species such as Sparisoma cretense and Mycteroperca fusca, weremore abundant and with higher frequency of occurrence inside the reserve and thedusky grouper, a widely targeted species across its range was exclusively recorded inside the reserve area, but with very low frequency and abundance. Although this study provided base-line data for ecological management purposesit is essential that further quantitative studies be conducted on densities, size structure aswell in settlement and recruitment processes, to fully acknowledge the inshore fish communities inhabiting the island. The paucity of information obtained till date on reef fish communities ofMadeira Island can be highlighted as a failure in the establishment and assessment ofthe effects of human activities on coastal reefs resources. Hence, the combination present results with the existing from few previous works will help understanding of the coastal reefs communities of Madeira Island. O presente trabalho visou o estudo das comunidades de peixes dos recifesrochosos da costa Sul da Ilha da Madeira com a finalidade de obter dados de referênciasobre a estrutura dos ictiopovoamentos que habitam a estreita faixa rochosa do litoralmadeirense. As comunidades foram caracterizadas em termos de riqueza específica,composição, abundância, estrutura trófica, espacial, demográfica e dinâmica sazonal,considerando os factores profundidade, tipo de substrato e localidade. Utilizaram-se trêsmétodos de contagem visuais (transecto, ponto fixo e visual fast count ),frequentemente utilizados em estudos semelhantes realizados noutras regiões do planeta,mas que aqui foram pela primeira vez aplicados em simultâneo, testando a suaeficiência e desempenho para avaliação das comunidades de peixes existentes, bemcomo uma revisão e actualização acerca deste tipo de metodologias. Avaliou-se o graude protecção das comunidades ictiológicas da Reserva Marinha do Garajau, estimandoos eventuais benefícios das medidas de protecção existentes e investigou-se também ainfluencia de determinadas intervenções humanas como é o caso da implantação deenrocamentos ao longo do litoral madeirense na estrutura das comunidades ictiológicasque estes locais agregam. Pretendeu-se também avaliar e evidenciar uma lista dosmaiores problemas associados à gestão dos recursos ictiológicos costeiros da Ilha daMadeira, identificando os parâmetros mais adequados a serem usados em decorrentesprojectos de monitorização dessas comunidades. O período de amostragem decorreu entre a Primavera de 2002 e a Primavera de 2004, em três localidades da costa Sul da Ilha da Madeira, numa área marinha protegida - Reserva Marinha do Garajau; uma área natural não protegida - Caniçal e uma área costeira submetida a intervenção humana, artificial - o enrocamento do aeroporto da Madeira.
Tipo de Documento
Tese de Doutoramento
Orientador(es) Almeida, Armando J., 1951-; Sedberry, George R., 1950-
Orientador(es) Almeida, Armando J., 1951-; Sedberry, George R., 1950-
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